I have an apple usb keybord for my ubuntu 12.04. I remaped command left key to control for convenience. And now I switch between apps with alt-tab and between tabs within one app with ctrl-tab. It's normal but not comfortable and painless.

It would be ideally to remap shortcuts as opposite: ctrl+tab - switching between apps, alt+tab - between tabs. Can I do it? xmodmap?

UPDATE: here is a screenshot of settings which I apply, restarted but it hasn't changed: